This invention relates to the field of physical therapy, and provides an apparatus and method for exercising the joints of the human foot following injury or surgery.
Conventional medical doctrine formerly taught that one should immobilize a joint following injury or surgery, to allow the joint to heal properly. More recently, physicians have recognized that doing just the opposite will cause a joint to heal more quickly and more completely. The term "continuous passive motion", also called "CPM", denotes the method whereby the joint undergoes continuous, artificially-induced, rhythmic movements, for the purpose of rehabilitation of the joint. Instead of holding a joint (such as a knee, an elbow, a finger joint, or a toe) immobile in a cast, one keeps the joint in slow, continuous, constrained motion. Medical practitioners have found that CPM overcomes the tendency of muscle to degenerate. One can effectively use CPM very soon after an accident or operation, and can thus maintain freedom of movement of the joint well before the muscle has regained the ability to function by itself.
Various patents show CPM devices of the prior art. For example, U.S. Pat. No. 5,010,878 shows a device specifically designed to impart continuous passive motion to the toes. In the patented device, a rod attaches to the patient's toes and moves them back and forth.
U.S. Pat. No. 4,862,875 shows another device which provides CPM for the foot, and which has separate means for lifting the toes.
Other examples of CPM devices, not necessarily directed to the toes, appear in U.S. Pat. Nos. 4,875,469, 4,716,889, 4,945,902, 4,637,379, 4,842,265, 4,558,692, and 3,789,836.
Experience in the field of toe CPM has shown that, for best results, the heel should flex at least about 40.degree. relative to the toes. While this amount of flexing provides the best therapy, it also creates substantial discomfort for the patient. Moreover, most of the toe CPM devices of the prior art do not move the heel at all, but instead move the toes only. With toe motion only, the task of generating a rotation of 40.degree. becomes difficult and uncomfortable for the patient.
More significantly, the devices of the prior art, which move the toes only, do not move the toes in an anatomically correct path. Some such devices tend to allow the toe to move from side to side, while flexing the joint. Other devices aim to move the toe joint in a circular motion, simulating the natural movements of the joint. But, in practice, the toe joint does not move in a perfectly circular path. By moving the joint in an exactly circular path, one does not replicate normal conditions of movement of the joint.
The present invention represents an improvement over the prior art, in that it provides both heel and toe movement, and generates the relative flexing required for proper therapy, while maintaining a high level of comfort for the patient. The present invention moves the toe joint in an anatomically correct path, which closely simulates the movements experienced during normal walking.
The invention includes an apparatus which precisely regulates the travel of a toe plate, in relation to the movement of the foot support plate. By appropriate selection of design parameters, one can insure that the toe plate will flex at exactly the right moment to produce the desired amount of flexing. The patient can control the maximum angles of movement and the speed of the device by using suitable controls mounted on the housing for the CPM device.